There is conventionally known a developing cartridge including a developing roller. The developing cartridge is detachably attached to an image forming apparatus.
For example, the developing cartridge includes a gear rotatable from a first position to a second position, and a protrusion provided at the gear. The protrusion moves together with the rotation of the gear and contacts a lever provided at the image forming apparatus. The lever moves when the lever contacts the protrusion. The image forming apparatus detects the movement of the lever to determine specification of the developing cartridge currently attached thereto.